Only use cDAC on platforms where we implement functionality to get an export symbol

Author: elinor-fung

src/coreclr/debug/daccess/daccess.cpp

@@ -30,6 +30,8 @@
 #include <dactablerva.h>
 #else
 extern "C" bool TryGetSymbol(ICorDebugDataTarget* dataTarget, uint64_t baseAddress, const char* symbolName, uint64_t* symbolAddress);
+// cDAC depends on symbol lookup to find the contract descriptor
+#define CAN_USE_CDAC
 #endif
 
 #include "dwbucketmanager.hpp"
@@ -5493,6 +5495,8 @@ ClrDataAccess::Initialize(void)
     IfFailRet(GetDacGlobalValues());
     IfFailRet(DacGetHostVtPtrs());
 
+// TODO: [cdac] TryGetSymbol is only implemented for Linux, OSX, and Windows.
+#ifdef CAN_USE_CDAC
     CLRConfigNoCache enable = CLRConfigNoCache::Get("ENABLE_CDAC");
     if (enable.IsSet())
     {
@@ -5513,6 +5517,7 @@ ClrDataAccess::Initialize(void)
             }
         }
     }
+#endif
 
     //
     // DAC is now setup and ready to use
@@ -6945,7 +6950,7 @@ GetDacTableAddress(ICorDebugDataTarget* dataTarget, ULONG64 baseAddress, PULONG6
         return E_INVALIDARG;
     }
 #endif
-    // On MacOS, FreeBSD or NetBSD use the RVA include file
+    // On FreeBSD, NetBSD, or SunOS use the RVA include file
     *dacTableAddress = baseAddress + DAC_TABLE_RVA;
 #else
     // Otherwise, try to get the dac table address via the export symbol